Hi. I was wondering how you determine whether or not you are at constant velocity in an airfact. THe IMU I'm getting comes with accelerometers which I never really planned a use for, but they're there so might as well use them how I can. I was thinking about using them to measure the inclination for the compass whenever the plane is at constant velocity but I am not sure how to determine that.
THe only way I could think of was the measring airspeed with the pitot tube but this is dependent on whether the wind is changing or not since if the wind is slowing down as fast as your plane is speed up you still measure zero speed when you are actually accelerating. Do you just assume the wind is essentially at constant speed (or changing slowly enough to assume that?) Or does it just fall apart?
On that note, my main source of resetting the roll/pitch gyro bias errors were IR horizon sensors that would reset the roll/pitch to zero whenever they detected such. But they'd have to be matched and thermopiles are far too expensive to buy a bunch and try and match a few, except I am not quite sure how to match them either (in analog) due to their different offsets and gains without a LOT of trial and error. It's another reason I'd like to use the accelerometers somehow (to allow roll/pitch reset whenever the plane is cruising rather than just whenever the roll/pitch crosses zero).
I suppose GPS could also be used to determine constant velocity, though I don't know how accurate it would be for that and it'd have to be fairly accurate to not distort inclination readings from the accelerometer. I've never quite trusted GPS and would at least like to augment it with something.
Let's also ignore the case of the wind accelerating in an axis where the pitot tube doesn't measure airspeed for now...
THe only way I could think of was the measring airspeed with the pitot tube but this is dependent on whether the wind is changing or not since if the wind is slowing down as fast as your plane is speed up you still measure zero speed when you are actually accelerating. Do you just assume the wind is essentially at constant speed (or changing slowly enough to assume that?) Or does it just fall apart?
On that note, my main source of resetting the roll/pitch gyro bias errors were IR horizon sensors that would reset the roll/pitch to zero whenever they detected such. But they'd have to be matched and thermopiles are far too expensive to buy a bunch and try and match a few, except I am not quite sure how to match them either (in analog) due to their different offsets and gains without a LOT of trial and error. It's another reason I'd like to use the accelerometers somehow (to allow roll/pitch reset whenever the plane is cruising rather than just whenever the roll/pitch crosses zero).
I suppose GPS could also be used to determine constant velocity, though I don't know how accurate it would be for that and it'd have to be fairly accurate to not distort inclination readings from the accelerometer. I've never quite trusted GPS and would at least like to augment it with something.
Let's also ignore the case of the wind accelerating in an axis where the pitot tube doesn't measure airspeed for now...
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